This application claims the priority of German Application No. 101 27 597.8 filed May 30, 2001, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a method for manufacturing spray diffusers which have flow compartments and connected mouthpieces having a narrowed cross section for the discharge of the liquid to be diffused and which are manufactured using multi-part molds whose hollow spaces in their negative form correspond to the outer and inner dimensions of the spray diffusers and are filled with liquid or thixotropic manufacturing material that is then made to solidify.
In the manufacture of spray diffusers that are produced using a casting process, providing cores for the creation of the internal configuration is known, while the outer configuration, especially with the manufacture of ceramic nozzles, is produced using plaster molds. The cores are destroyed after the casting operation; the plaster molds can be used more often.
FIG. 2 schematically shows the appearance of a mold for the manufacture of ceramic nozzles according to the prior art. One can see that the interface between the core (not depicted here in detail) and a mouthpiece plug 50 lies within the area of the cross-sectional narrowing of flow chamber 51 to outlet channel 52 of mouthpiece 53. A configuration of this type is selected in consideration of the finished moldability. The interface between outer mold part 54, which is adjacent to mouthpiece 50, which continues with a further upper molded part in a manner not shown in greater detail, is situated in the area of the outlet edge of mouthpiece 53. Since the mold parts can never fit against each other exactly, mold parting seams result at these mold parting places because the manufacturing material runs into these parting gaps of the molds. At the two aforementioned places, at outlet edge 55 and at the transition on flow chamber 51 to the narrowed cross-section of mouthpiece 53, thus at position 56, mold parting seams are therefore produced which as a rule must be manually removed after extraction of the cast spray diffuser. Since these places 55 and 56 in spray diffusers are decisive for the quality and function of the spray diffuser because the flow path and interruption of the spray stream are affected here, the finishing work must be carried out thoroughly and at great expense. To explain this, reference is made in this connection to the fact that spray diffuser 57, shown in FIG. 2, is a swirl spray diffuser for producing a hollow-cone spray stream, the liquid to be sprayed being fed in the direction of arrow 58. The liquid that is fed in principle enters tangentially into flow chamber 51, which as a rule is rotational symmetric, is set in rotation by the tangential entry so that a liquid film forms on the walls and then transitions into mouthpiece 53 at position 56 and, by reversal in the direction of rotation, transitions into a tangential and axial speed at outlet edge 55 and forms a liquid screen in the shape of a hollow cone that disintegrates into droplets just past outlet edge 55. It therefore depends very much on the exact observance of the internal configuration.
An object of the present invention is to propose a manufacturing method, and a mold suitable for this method, with which it is possible to prevent to a great extent the expensive finishing work on the aforementioned critical areas. To achieve this objective, it is provided in a method of the type mentioned at the outset that the outlet edges of the mouthpiece and the transitional areas of the inner wall between flow chamber and mouthpiece are each formed out wall areas of one-piece molded parts that abut against the adjacent molded parts outside these wall areas. By this configuration, the two critical areas 55 and 56 are depicted in FIG. 2 are produced without mold parting seams since there are no mold parting seams located within these areas. The mold parting places are situated at non-critical places, so that secondary machining does not require any great expense.
In a further development of certain preferred embodiments of the present invention, a mold for carrying out the method of the aforementioned type can be provided which is provided with a core and at least one mouthpiece plug, as is also the case for the state of the art. However, in contrast to the prior art, the mouthpiece plug is now provided with the negative in the shape of a circumferential groove and is configured in such a manner that it abuts against adjacent molded parts only outside this groove.
In a further development of certain preferred embodiments of the present invention, it is also advantageously possible to provide the mouthpiece plug with a ring whose perimeter corresponds to the transitional area of the inner wall between flow chamber and mouthpiece. This ring, which is adapted to the expanding inner contour of the flow chamber that is situated before the mouthpiece, can, as will be explained in greater detail below, be placed by the inner chamber of the mold onto the mouthpiece so that the mold release operation is not hindered. It is thus appropriate in a further development of the invention to place this ring on an axially projecting pin of the mouthpiece plug and hold it there, it being possible to provide this projecting pin with a non-circular cross-section in order to prevent the ring from twisting in relation to the mouthpiece plug. This projecting pin can also engage into the core, so that a twisting between mouthpiece and supplementary ring is safely avoided, and the manufacture of a cast spray diffuser is possible without problems. After mold release it is only necessary, as already mentioned, to remove the mold parting seams, which, however, are not located on the critical areas and therefore are relatively simple to remove without affecting the functional quality of the diffuser.
The present invention is described on the basis of embodiments in the drawing and is explained in the following.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.